THE IMPORTANCE OF CONVEYING IN A DECANTER CENTRIFUGE

摘要

Decanter centrifuges are often used for sludge dewatering in chemical industries and municipal waste water treatment facilities. Due to centrifugal force, the sludge is settled and dewatered in the cylindrical section of the centrifuge. The rotating screw in the decanter conveys the sludge from the cylindrical to the conical part to the solid outlet. For conveyance to occur, the screw and bowl of the decanter must have a specific differential speed to bring about the desired residence time and conveying pattern. Rheological behavior and decanter design also have a significant effect on the process. In addition, the back up of material resulting from improper conveying can influence the dewatering and sedimentation of the sludge.The paper will highlight how the conveying of solids in a decanter centrifuge affects dewatering at the conical part, clarifying at the cylindrical part, and how the conveying itself causes abrasion effects. To improve the conveying process, studies were conducted on a full-size decanter centrifuge at a chemical plant. The results of these studies will be presented. This case study will explain the basic processing steps in a decanter centrifuge, and their interaction. Torque measurements will be discussed because they provide helpful information about sludge behavior during conveyance. Process parameter and design changes will be presented as a means of improving the conveying process.